1. Field of the Invention
This invention relates to a process for hydrogenating low rank coal to liquid and gaseous hydrocarbons.
2. Description of the Prior Art
A number of ebullated bed processes have been developed for the conversion of coal to liquid and gaseous hydrocarbons. These processes include one requiring two catalytic stages U.S. Pat. No. 3,700,584, a second process having a countercurrent transfer of catalyst from the second stage to the first stage (U.S. Pat. No. 3,679,573), and a single stage non-catalytic technique (U.S. Pat. No. 3,617,465). Satisfactory results can consistently be obtained with these methods with feeds other than low rank coals. However, when low rank coals are treated, conversion and, as a result, operability have not been satisfactory. These unsatisfactory results are caused by the relatively low hydrogenation rates of these coals and, in the case of the catalytic processes, by the rapid inactivation of the catalyst by the metallic impurities contained in the coal and carbon deposition.